用素土桩挤密法处理陇东湿陷性黄土地基     

缪祥生  俞宗卫  于丽羽 《地球科学与环境学报》1994,(2)

素土桩挤密地基由桩间挤密土和回填素土夯实的桩体组成，它是一种人工“复合地基”。其作用是通过素土桩挤密法提高地基土的密实度，从而对湿陷性黄土达到消除浅部或深部的部分或全部湿陷性的作用，并改善地基承载能力，减少地基变形。本文通过现场单桩、群桩单元体轻便触探、小环刀深层取样、开剖取样等方法对场地地基土挤密前、后干重度和压实系数进行了对比分析，判定用素土桩挤密法处理陇东湿陷性黄土地基的可行性。  相似文献   

Luminescence dating of sand–loess sequences and response of Mu Us and Otindag sand fields (north China) to climatic changes     

Yali Zhou  Huayu Lu  Jiafu Zhang  Joseph A. Mason  Liping Zhou 《第四纪科学杂志》2009,24(4):336-344

The sand–loess transition zone in north China is sensitive to climate change, and is an ideal place to investigate past environmental changes. However, past climate change at millennial–centennial timescales in this region has not been well reconstructed because of limited numerical dating. Alternations of sandy loam soils with aeolian sand layers in the Mu Us and Otindag sand fields, which lie along the sand–loess transition zone, indicate multiple intervals of dune activity and stability. This change is probably a response to variations of the East Asian monsoon climate during the late Quaternary. The single aliquot regeneration (SAR) optically stimulated luminescence (OSL) dating protocol, which has been successfully applied to aeolian deposits worldwide, is applied to these two sand fields in this study. The OSL ages provide reliable constraints for reconstruction of past climate changes at suborbital timescale. Sections in both sand fields contain aeolian sand beds recording millennial‐scale episodes of dry climate and widespread dune activation, including episodes at about the same time as Heinrich Event 5 and the Younger Dryas in the North Atlantic region. These results demonstrate the potential of aeolian sediments in semi‐arid north China to record millennial‐scale climatic events, and also suggest that dry–wet climate variation at the desert margin in China may be linked to climatic change elsewhere in the Northern Hemisphere, through atmospheric circulation. This article was published online on 27 November 2008. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected (16 December 2008). Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

一种准确通用的台风路径预报模式   总被引：1，自引：0，他引：1  

朱敬海  潘杰丽 《海洋预报》2007,24(1):69-74

应用天气学理论,对台风云图的晴空区轴线制约台风移动的规律进行物理解释。根据台风云团与晴空区之间存在的干、湿梯度力和推动台风前进的惯性力的互相关系,建立台风移向预报方程和轨迹预报方程,分析论证了台风移向变化的物理过程,把影响台风移动的复杂因子转化为单一的预报因子。  相似文献   

Seasonal Variation in the Biomass of Marine Macrophyta from Greek Coasts     

S. Haritonidis    G. Nikolaidis  I. Tsekos 《Marine Ecology》1986,7(4):359-370

Abstract. The marine plant communities of the littoral zone in different biotopes of the Greek coasts were investigated in 1980-81. Seasonal distribution and variation of marine plant biomass were assessed. The communities of Cystoseira crinita and C. compressa were outstanding with maximum biomass during the summer months. Corallina officinalis and Pterocladia capillacea + Viva rigida communities predominated with maximum biomass in autumn and exhibited a decrease in winter, except in stressed biotopes. The species diversity and productivity of seaweeds along the Greek coasts are interpreted in relation to a number of environmental parameters.  相似文献   

青岛近海地区SO2和SO42-干沉降速率的季节变化     

王泽杰  祁建华  于丽敏  高会旺 《海洋湖沼通报》2006,(4):86-93

用小麦岛和团岛观测站提供的青岛近海气象和水温资料,以适于SO2气体和硫酸盐(SO42-)气溶胶的干沉降模型研究了模型中的输送阻尼对两种污染物质干沉降速率的贡献,并计算了2003年青岛近海地区两种污染物质干沉降速率的季节变化。结果表明:对SO2而言,粘性副层传输系数对沉降速率的贡献大于空气动力学传输系数;对于SO42-,空气动力学传输系数对沉降速率的贡献要大于表面传输系数。SO2和SO42-的干沉降速率变化范围分别为0.187~0.868cm/s和0.188~0.532cm/s。两种污染物质干沉降速率的四季变化有相似的规律,即冬季>秋季>春季>夏季。  相似文献   

模型沙干重度的变化规律及其在泥沙模型试验中的作用     

韩玉芳  陈志昌 《海岸工程》2003,22(1):1-7

模型沙干重度在动床模型试验中是影响起动流速比尺和冲淤时间比尺的重要参数，其随淤积历时、粒径变化、埋置深浅和加工方法的不同有着不同的变化规律。通过试验，结合已有的成果，对模型沙干重度受以上几种因素的影响进行了研究，并进一步分析了其变化规律在动床模型试验中的作用。  相似文献   

A Study on Hydroelastic Response of Box-Type Very Large Floating Structures     

王志军  李润培  舒志 《中国海洋工程》2001,(3):345-354

The application of very large floating structure (VLFS) to the utilization of ocean space and exploitation of ocean resources has become one of the issues of great interest in international ocean engineering field. Owing to the advantage of simplicity in structure and low cost of construction and maintenance, box-type VLFS can be used in the calm water area near the coast as the structure configuration of floating airport. In this paper, a 3D linear hydroelastic theory is used to study the dynamic response of box-type VLFS in sinusoidal regular waves. A beam model and a 3D FEM model are respectively employed to describe the dynamic characteristics of the box-type structure in vacuum. A hydrodynamic model (3D potential theory of flexible body) is applied to investigate the effect of different dry models on the hydroelastic response of box-type structure. Based on the calculation of hydroelastic response in regular waves, the rigid body motion displacement, flexible deflection, and the short term and long  相似文献   

太原盆地农田区大气降尘对土壤重金属元素 累积的影响及其来源探讨   总被引：1，自引：0，他引：1  

赖木收  杨忠芳  王洪翠  周继华  王建武 《地质通报》2008,27(2):240-245

通过研究太原盆地大气干湿沉降中重金属元素的含量分布特征及年输入通量,讨论其对土壤中重金属元素累积的影响。同时采用富集因子法探讨降尘物质的来源。研究结果表明,降尘中重金属元素As、Cd主要来源于人为活动,Pb的来源可能是人为源和自然源。而Hg则主要来源于自然源。  相似文献   

Modelling of the vertical fluxes of nitric acid,ammonia, and ammonium nitrate     

Gerhard Kramm  Ralph Dlugi 《Journal of Atmospheric Chemistry》1994,18(4):319-357

Results from numerical investigations regarding the exchange of HNO₃, NH₃, and NH₄NO₃ between the atmosphere and the biosphere are presented. The investigations were performed with a modified inferential method which is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these nitrogen compounds. This modified inferential method calculates the micrometeorological quantities (such as the friction velocity and the fluxes of sensible and latent heat), the height-invariant fluxes of the composed chemically conservative trace species with group concentrationsc ₁=[HNO₃]+[NH₄NO₃] (total nitrate),c ₂=[NH₃]+[NH₄NO₃] (total ammonia), andc ₃=[HNO₃]-[NH₃] as well as the fluxes of the individual nitrogen compounds. The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The modified inferential method requires only the data of wind velocity, temperature, humidity and concentrations (HNO₃, NH₃, and NH₄NO₃) measured at a reference height by stations of a monitoring network.  相似文献   

硫铅酸盐“S”型瞬凝水泥干法护壁堵漏技术研究          下载免费PDF全文

彭振斌 《探矿工程》1995,(2):41-42,60

介绍了硫铝酸盐“Ｓ”型瞬凝水泥干法者漏时使用的配方,阐述了输送工具和扫孔钻具的设计以及灌注工艺技术。  相似文献